docs: def import_issuers(self, new_issuers):
          """
          Add the given issuers/issuer to the corpus.
          If any of the given issuer-ids already exists, a suffix is appended so it is unique.
  
          Args:
              issuers (list): Either a list of or a single :py:class:`audiomate.issuers.Issuer`.
  
          Returns:
              dict: A dictionary containing idx mappings (old-issuer-idx/issuer-instance).
                    If a issuer is imported, whose id already exists this mapping can be used to check
                    the new id.
          """
  
          if isinstance(new_issuers, issuers.Issuer):
              new_issuers = [new_issuers]
  
          idx_mapping = {}
  
          for issuer in new_issuers:
              idx_mapping[issuer.idx] = issuer
  
              # Add index to idx if already existing
              if issuer.idx in self._issuers.keys():
                  issuer.idx = naming.index_name_if_in_list(issuer.idx, self._issuers.keys())
  
              self._issuers[issuer.idx] = issuer
  
          return idx_mapping